At the foot of the mountain, Abraham states that "we" will return. He says nothing about returning alone which suggests that Abraham knew the two of them would return even if God didn't. The Sages of Judaism claim that it is a prophecy uttered unknowingly by Abraham.The response of God to Abraham's obedience leads me to believe that God did not know of a certainty or necessarily that Abraham would obey him...Now I know..
He said, “Do not lay your hand on the boy or do anything to him, for now I know that you fear God, since you have not withheld your son, your only son, from me.”
Rashi explains that God is not actually asking Abraham to sacrifice his son. It doesn't appear in the Hebrew. It is only the translators who assume this to be the case. For some unknown reason, God allows Abraham to believe that he must sacrifice his son.
God only says "Bring him up". Abraham assumes it is to slaughter him. Rashi explains that it is to justify Abraham before Satan and other nations. Satan wouldn't believe it unless Abraham was ready to drive the knife down to kill his son.